More particularly the present invention relates to a handwheel for valve provided with an indicator of level of opening which exploits the particular kinematism apt to produce, univocally and ruggedly, the indication of the level of opening of the valve and to allow, at the same time, easy reading of the position of opening of the same.
As is known, hydraulic valves are typically provided with manoeuvre members defined by a lever or by a handwheel apt to allow the rotation movement of a sphere or translation of a gate or globe to perform the opening/closure of the valve and the choking of the same, so as to regulate the parameters of the flow processed.
For example, in the case of shut-off valves, the important positions are only two, i.e. the position of opening and of closure of the valve and, therefore, an indication of the intermediate positions is not necessary.
Contrarily, in the case of valves of calibration or balancing or the like, for the correct use of the valve it is appropriate to be able to allow the user to read, simply and easily, the degree of opening/closure of the valve. In some cases actual industry regulations impose the use of an indicator of the level of opening integrated with the valve (for example BS7350 (British Standard) for globe balancing valves).
Considering the valves wherein the shutter is actuated by means of a rod or screw, the movement of opening/closure of the valve is of the rotary type and performed by imparting on said rod or screw a certain number of turns, for example by means of a handwheel, in such a way as to allow the passage from a position of maximum opening to one of maximum closure.
In globe balancing valves, for example, the manoeuvre handwheel has to be provided with an indicator apt to indicate the degree of opening and, consequently, the position of regulation of the same valve with the precision of the tenth of turn. For example the indication 4.2 corresponds to an opening of four whole turns plus two tenths of a turn, i.e. (360°×4)+(36°×2)=1512° of rotation of the manoeuvre member.
Multiple mechanisms and kinematisms are traditionally used to form the indicators of the degree of opening of a hydraulic valve.
Generally the degree of opening of the valve is indicated by means of two figures (the figure of the units and the figure of the decimals) displayed in two different windows or in two different positions of the manoeuvre/regulation handwheel.
In most cases the figure indicating the whole number of turns of opening is displayed inside a window formed on the handwheel, located either in the lateral part or in the upper part of the same handwheel.
A known handwheel with indicator of the degree of opening is schematised in FIG. 1 and has the figure indicating the whole number of turns written on the base of a cylindrical wheel 10, hinged on an axis integral with a knob 11, and actuated by means of a mechanism of the pin-gear wheel (FIG. 1) wherein said driven member or wheel has a series of equally distanced compartments 12 inside whereof a rung 14 engages, integral with a fixed base 16 whereon the decimal figures are indicated. The rung 14 meshes with a compartment 12 only once per turn, making the driven wheel 10 rotate through the angular interval necessary for revealing the next figure.
According to another known embodiment schematised in FIG. 2 the whole and decimal figures are given on the lateral surface of a cylindrical drum 18 which is defined by two coaxial idle wheels 18′ and 18″ whereon the figures indicating the whole number of turns and the decimal figures are given respectively. The cylindrical drum 18 is set in rotation by means of a drive wheel 19 provided with a rung 19′ apt to engage with a cogged profile of the idle wheel 18′ and a cogged ring nut 19″ apt to mesh with a conjoined cogged profile of the idle wheel 18″.
According to further known embodiment solutions, such as for example the one schematised in FIG. 3, the figure indicating the tenths of a turn is printed on a ring 20 integral with a mobile part 21 of the manoeuvre handwheel, while the figure indicating the units is given on a wheel 22 actuated by a mechanism of the pin-gear wheel.
However these embodiment solutions, exploiting a discontinuous coupling between the driven member and the driving member, require optimal manufacture and high precision in the production of the components apt to enter into a coupling one with the other. This entails a disadvantage linked to the fact that imprecise manufacture may entail the “slipping” of some meshings during the phases of manoeuvre with consequent imprecisions in the indication of the figures relating to the degree of opening of the valve.
A further disadvantage of the aforesaid known embodiment solutions is represented by the fact that the wheel bearing the figures indicating the whole number of turns or units is always an idle wheel and, consequently, maintains the correct position as a function only of the static friction appropriately designed and produced. Any imprecision whatsoever in manufacture can entail an increase in the clearances between the couplings, reducing said friction with correlated random movements of the driven wheel and consequent imprecisions in the indication of the degree of opening of the valve.
Another technical solution is schematised in FIG. 4. The figure indicating the tenths of a turn, given on the mobile part 23 of the manoeuvre handwheel, is displayed through a window 24 formed on a fixed base 25 of the same manoeuvre handwheel, while the figure indicating the whole numbers is printed on a slider 26 coupled to the mobile part 23 via a mechanism of the screw-lead screw type which performs the movement and consequent display of the figures.
However these traditional solutions, as well as disadvantages linked to the presence of idle wheels, can also have further major disadvantages linked, for example, to the fact that the movement and the display of the figures are actuated by means of a continuous coupling in which the figure of the units is displayed gradually and continuously, reducing the ease of reading.
Similar disadvantages can also be found in US2013/0133763 in which reference is made to a handwheel for valve provided with an indicator of position and elements of magnetic coupling, with said handwheel comprising a container element provided with a support element, a first shaft with a motor gear, a rotating element of connection between the support element and the first shaft, a train of gears coupled to the motor gear and configured to move a position indicator needle, a first magnet attached to the support element, a second magnet attached to an assembly device for the valve control handwheel and with said first and second magnets configured to maintain the support element in a stationary position with respect to the assembly device for the valve control handwheel.